When a congestion state of people is monitored, an overall state can be intuitively determined by checking downward view image data for a wide range which is looked down from immediately above, rather than by checking a state while switching imaging data captured by imaging apparatuses which are installed at various locations.
Patent Literature 1 describes a downward view image data display technique for a train crew member to monitor the states of passengers getting off a train onto a platform and passengers getting on the train from the platform. In Patent Literature 1, imaging data of a plurality of cameras installed on the top of entrance/exit doors of each car are transformed into downward view image data, and the pieces of downward view image data are combined to display panoramic image data for the side of all cars on a monitoring terminal.